The present invention relates to a differential limiting device for a differential device, and particularly a differential limiting device for a differential device having a clutch mechanism.
By convention, a differential device is provide with a differential limiting device which additionally applies a predetermined differential limiting torque as an initial torque, and when one of the output shafts slips, it transmits a torque to the other output shaft by bypassing the one of output shaft.
A differential limiting device comprising a hydraulic multiple disc clutch is known. In a center differential device of the planetary gear type, disclosed in Japanese Patent Unexamined Publication No. Hei. 5-112149, a hydraulic multiple disc clutch is provided between a carrier and a drive shaft. The hydraulic multiple disc clutch generates a differential limiting torque depending on a slip of the rear wheel or the like. In this hydraulic multiple disc clutch, a differential limiting torque is generated by a multiple disc type clutch mechanism. Accordingly, a relatively large torque can be generated.
On the other hand, the hydraulic multiple disc clutch needs a hydraulic mechanism for carrying out an engaging control of the clutch mechanism. Accordingly, the structure thereof becomes complicated. In some layout of the differential device, it is difficult to secure a hydraulic pressure source.
Accordingly, it is an object of the present invention to provide a differential limiting device for a differential device which is capable of performing an engaging control of a multiple disc clutch mechanism with a simple structure.
The above-mentioned object can be attained by a differential limiting device for a differential device which limits relative rotations of a shaft for inputting and outputting drive power to a carrier and the carrier aligned with the shaft, the differential limiting device, according to the present invention, comprising:
a clutch mechanism aligned with the shaft for engaging the shaft and the carrier;
a ring-shaped clutch piston being rotated together with the shaft and being retractively movable in an axial direction of the shaft, thereby pressing the clutch mechanism;
protruded parts protruded in the axial direction and each having an end that is confronted with the clutch piston; and
cam crests formed on a surface of the clutch piston and confronted with the protruded parts, the cam crests being brought in sliding contact with the ends of the protruded parts respectively;
wherein the protruded parts retractively move along the cam crests of the cam part to move the clutch piston in the axial direction when the carrier and the shaft relatively rotate.
In an embodiment of the differential limiting device, it is advantageous that the differential device is a planetary gear type differential device including a sun gear provided on the shaft, pinions being meshed with the sun gear, and pinion shafts for rotatably supporting the pinions on the carrier, and wherein the protruded parts are formed with the pinion shafts protruded from the carrier.
In addition, in an embodiment of the differential limiting device, it is advantageous that a maximum shift of the clutch piston by the cam crests in the axial direction is smaller than a stroke length of the clutch piston within which the clutch piston is refractively movable, and the cam crests are continuously formed in a ring shape.
Further, in an embodiment of the differential limiting device, it is advantageous that each of the cam crests has cam surfaces that are configured to be asymmetrical with respect to a direction of its rotation relative to the protruded part.
Furthermore, an embodiment of the differential limiting device according to the present invention may further comprises:
elastic members interposed between the clutch piston and the clutch mechanism for pressing the clutch mechanism.
Moreover, an embodiment of the differential limiting device according to the present invention may further comprises:
an elastic member placed in the clutch mechanism.